Role Of Antimony In Copper Electrolyte Purification Mechanism And Valence State Translation Way Of That

Copper electrolyte self-purification is defined that, the electrolyte can bepurificated according to the coprecipitation reaction among impurities As, Sb and Bi inelectrolyte, which has a number of advantages: high purification efficiency; withoutintroducing new material; simple operation, thus, copper electrolyte self-purificationhas a wide prospect of application. But there have always existed many theories aboutthe self-purification mechanism, and there is no unified understanding.This paper investigates the influences of initial Sb（Ⅲ）, Sb（Ⅴ） ions concentrationand Sb（Ⅲ）/Sb（Ⅴ） mole ratio on removal of As, Sb and Bi impurities removal fromcopper electrolyte based on coprecipitation by adding a various concentration ofSb（Ⅲ）, Sb（Ⅴ） ion respectively, or at the same time in a synthetic electrolyte containingH₂SO₄, Cu²⁺, As and Bi under a certain condition. The purified electrolyte was thenfiltered to remove the precipitate. The content of the filtrate elements was determined.The precipitate structure, morphology and composition were analyzed by means ofchemical analysis, XRD, SEM, TEM and IR spectroscopy in order to reveal the role ofantimony in As, Sb and Bi impurities removal mechanism from copper electrolyte. Sbcontent in synthetic electrolyte under different conditions was determined, also thevalence state was traced to reveal the redox rule of Sb for the first time. Meanwhile,the electrochemical behavior of Sb in acidic solution was studied by means ofelectrochemical test. Finally, the antimony valence transformation way was proposed.The results show that, As, Sb, Bi impurities can be removed from copperelectroytes by Sb（Ⅲ） and Sb（Ⅴ）, but the removal effect of the latter is morepronounced. When Sb（Ⅲ） and Sb（Ⅴ） concentrations reach1.2g/L, the removal ratesof Sb and Bi are higher, the former are48.02%and38.4%, and the latter are76.83%and79.2%, respectively. The removal mechanism by Sb（Ⅲ） can be summed as theprecipitate formed in electrolytes is composed of larger irregular lump, agglomeratedby fine lump, dendritic and floccus particles, in which the main phases are SbAsO₄, （Sb,As）₂O₃and amorphous phases. Antimonate, including AsSbO₄, BiSbO₄andBi3SbO7formed in electrolytes is the main reason of impurities removal. It can befound that precipitate is composed of large irregular lump, therefore, impurities can beremoved quickly, and the removal rate of As, Sb and Bi is higher.In copper electrolyte, antimony molar ratio has a major influence on the removalof As, Sb and Bi from electrolytes. When nSb（Ⅲ）/nSb（Ⅴ）is1:4, the removal of As and Sbis best. The removal rate of Sb is relatively high when the ratio ranges from1:4to4:1.When Sb（Ⅴ） content is higher, antimony formes and deposits in electrolytes mainly.The size of precipitate particles is larger, which makes the precipitates relatively easierto deposit in the electrolyte, resulting in the high removal rates of As, and Bi. With theincrease of Sb（Ⅲ） ion in electrolyte, Sb（Ⅴ） ions react with Sb（Ⅲ） ions to formantimony oxide when nSb（Ⅲ）/nSb（Ⅴ）is1:1. When Sb（Ⅲ） content is higher, the formationof arsenate plays a main role. The size of arsenate particles is smaller, which makes theprecipitates relatively harder to deposit in the electrolyte, resulting in the low removalrates of As, Sb and Bi. Thus, a proper amount of Sb（Ⅲ） ions are suggested to betransformed to Sb（Ⅴ） ions according to1:4in order to improve the purificationefficiency of copper electrolytes. Copper electrolyte self-purification is the result ofarsenate, antimony,（Sb,As）₂O₃and amorphous phases contained As, Sb, Bi forme anddeposit in electrolyte, and also the formation of antimony is the main reason.Sb（Ⅲ） and Sb（Ⅴ） can separately exist steady under room temperature withstanding. Sb（Ⅲ） is oxidated slightly in initial period under heating to65oC withstirring, and the Sb（Ⅲ） content remains constant later. Sb（Ⅲ） oxidation rate willsignificantly increase, when antimony is coexisting with antimony and bismuth.Antimony and Bimuth can be oxidated by hydrogen peroxide, but the oxidation rate ofAs is faster than Sb. After adding Sb（Ⅲ）, reduction peak appears near-0.13V in thecathodic process, oxidation peak appears near0.03V in the anodic process. Afteradding Sb（Ⅴ）, reduction peak appears near-0.1V in the cathodic process, oxidationpeak appears near0.05V in the anodic process.